What Causes A Chin Swelling And Tenderness With No Other Symptoms?

Hi Dr. Grief- I've noticed lately there's a bulge under my chin (right side, about 1" back from the front of my chin). It's a bit tender (perhaps from my touching it most of the day?). The bulge is about 1" in diameter and it protrudes when I swallow. I'm not having any current problems w/ colds or sinus infections, and I do not have any problems w/ acne. It doesn't feel hard. It feels like a firm flexed muscle. Any suggestions on what it could be? Thank you in advance. ~Gail